Our original hypothesis of the basic structure of riboflavin-binding protein (32,000 daltons) suggested two peptide units joined by dithio-bridges. This hypothesis was supported by the recovery of a 24,000 daltion unit with 2 carboxymethyl-cysteine residues (after controlled reduction and alkylation). Recently we have been able to separate RBP into 2 components by gel chromatography (without reduction) in SDS. No similar separation was achieved in 8 M urea of 6 M guanidine HC1. Determination of the nature of the above interaction is important to provide the basic information needed in studies of regions of homology with Pro-RBP and CRM isolated from livers of Rd Rd and rd rd chickens, respectively. The search for endoglycosidases capable of removing the oligoglycoside from the protein is continuing. The CHO-free protein will be used to study transportability to the yolk and mobility of SDS gels. The protein-free carbohydrate is required for quantitative structural studies and for determination of the role of CHO as an immuno-determinant(s) in the production of RBP antiserum. The RBP antiserum is used in detection and isolation (affinity chromatography) of Pro-RBP and CRM. BIBLIOGRAPHIC REFERENCES: Hammer, C.H., E.G. Buss, and C.O. Clagett. Avian Riboflavin IX. Qualitative action of a mutant gene in chicken on riboflavin-binding protein synthesis. Genetics 82:467-476. 1976. Benoff, F.H. and E.G. Buss. Water consumption and urine volume in polydipsic and normal White Leghorn chickens. Poultry Sci. 55:1140-1142. 1976.